1. Field of the Invention
The present invention relates to technologies for processing image data to be provided to image forming apparatuses such as electrophotographic or inkjet copiers and printers or the like, and particularly relates to image forming apparatuses and control methods thereof in which the amount of consumption of a recording agent such as toner or ink or the like is controlled.
2. Description of the Related Art
In image forming apparatuses that form images using an electrophotographic or inkjet method, the amounts of coloring material such as toner or ink are adjusted in response to image signals at the time of image formation. In these apparatuses it is common to provide a toner or ink consumption amount conserving mode that conserves running costs by reducing the consumption amounts of coloring material. Furthermore, in a case where image signals are input from an external source and an image is to be output, depending on characteristics of the image forming section of the printer, characteristics of the toner or ink, and the processing method for increasing the printing speed, sometimes a limit must be set on the consumption amount of toner or ink to be applied per unit of surface area. In such cases, a process is carried out of reducing the overall image signal levels to certain fixed limited values by matching the consumption amounts of toner or ink to the printing characteristics of the printer. As these processing methods, methods are known as described in Japanese Patent Laid-Open No. 2005-101934 for example in which the C, M, and Y image signal levels are reduced by a certain fixed ratio after under color removal. Furthermore, Japanese Patent Laid-Open No. 10-73978 describes a method in which the C, M, Y, and K image signal levels are reduced by a certain fixed ratio.
However, with the conventional method of limiting toner or ink amounts described in Japanese Patent Laid-Open No. 2005-101934, sometimes the gradation properties of dark areas are deteriorated and information that the image originally held is lost. This is caused by the range of color reproduction being narrowed due to reducing the image signal levels by the certain fixed ratio to limit the amounts of toner or ink.